Mycology

18. Which of the following organisms grows well in the presence of bird droppings? a. Blastomyces dermatitidis b. Histoplasma capsulatum c. Cryptococcus neoformans d. B and C

D.

2 types of fungi

Saprophytic = from the environment (dead organic matter) Parasitic = from living organisms

Describe the common features of opportunistic mycoses and the causative agents : Candidiasis

-Opportunistic mycoses are Mainly caused by OPPORTUNIST FUNGI, which are ubiquitous in environment (soil/plant) or part of normal flora, and seldom cause DZ with out some underlying predisposing factor, such as trauma or immunosuppression a) Candidiasis is a primary or secondary mycotic infection caused by members of the genus Candida, mainly C. albicans. b) Involvement may be localized to the mouth, throat, skin, scalp, vagina, fingers, nails, bronchi, lungs, or the gastrointestinal tract, or become systemic as in septicemia, endocarditis and meningitis. -In healthy individuals, Candida infections are usually cutaneous due to impaired epithelial barrier functions and occur most common in the newborn ("thrush") and the elderly. -Systemic candidiasis is usually seen in patients with cell-mediated immune deficiency. c) Diagnosis: -Histopathology - Candida appears as yeast cells (blastoconidia) or pseudo-hyphae in exudate. d) Treatment: -In poultry, copper sulfate in drinking water is a traditional treatment. Nystatin can be given in feed or water. -It is also used topically in mucosal and cutaneous forms of candidiasis of mammals, as are amphotericin B, -azoles, and flucytosine.

Characteristic of fungi

-abundant in soil, vegetation , and in water -perform extracellular digestion and obtain nutrients by absorb (chmoorgano-heterotropic) -no chloroplasts-not photosynthetic

How are fungi classified?

1. a. Traditionally, fungi are classified based on their morphological characteristics and sexual spore production. The kingdom Fungi comprises the Zygomycota, Ascomycota, Basidiomycota, and Deuteromycota. The first three groups produce sexual spores, but the deuteromycetes are "imperfect fungi" (or "fungi imperfecti"), which are characterized by production of septate mycelium and/or yeasts, and a sexual life cycle that is either unknown or absent. b. Currently, classification of fungi is based on molecular phylogenetic approaches and still evolving,which use PCR technique and DNA sequencing of fungi 18S rRNA gene. c. The kingdom Fungi is currently divided into seven phyla, which includes subkingdom Dikaryaconsisting of Ascomycota and Basidiomycota. The phylum Zygomycota (zygomycetes) is no longer accepted and now placed between two phyla. d. For anamorphic molds (Deuteromycota - not an officially recognized taxonomic group!), even in the absence of the teleomorph, they can be assigned to Ascomycota or Basidiomycota based on DNA sequences of anamorphs and molecular phylogenetic analysis.

Structures of Fungi= Hyphae

2 types of fungi : Molds and Yeast Hypha- -fundamental tube like structural units of MOLD -Septate=divided by cross wall -Aseptate-no cross wall Mycelium -a mass/mat of intertwined branching filaments (hyphae) forming Vegetative portion of fungus Thallus - in molds or fleshy fungi

1. Which of the following components is present in fungi? A. Ergosterol B. Chloroplast C. Cholesterol D. Peptidoglycan

A

16. Which of the following organisms produces an extremely large capsule, making it a useful identifying feature microscopically? The organism is often associated with feline nasal disease. a. Cryptococcus neoformans b. Histoplasma capsulatum c. Blastomyces dermatitidis d. Coccidioides immitis

A.

4. "Imperfect fungi" refer to organisms that ______________________. a. Have no known sexual states b. Have aseptate hyphae c. Cannot form a mold phase d. Cannot form a yeast phase.

A.

Growth of Hyphae on Agar based media

Aerial = growing or existing in air -Conidia or Sporangia (spores) Vegetatative - absorb nutrient

Describe the common features of opportunistic mycoses and the causative agents: Aspergillosis

Aspergillosis. a) Caused by Aspergillus fumigatus, which are ubiquitous saprophytic molds and common contaminant of food or litter. b) Aspergillosis are opportunistic mycosis that depend on impaired, overwhelmed, or bypassed host defenses. -It's mainly acquired from environmental sources, generally by inhalation or ingestion. -It can be pulmonary and disseminated infections, frequently involving kidneys and the central nervous system, like avian aspergillosis ("brooder pneumonia"), Canine rhinitis, Mycotic Keratitis (keratomycosis), and Mycotic Abortion in Cattle. c) In tissue, Aspergillus usually grows as dichotomous (continuous) branching septate hyphae at a 45° angle, but fruiting head (flask-shaped phialides) with pigmented conidia spores are seldom seen, except in aerated cavities (e.g., nasal passages, air sacs, and cavitary lesions) that are important diagnostic features.

21. Which of the following statement describing opportunistic fungi is FALSE? a. Opportunistic fungi are ubiquitous in environment (soil/plant) or part of the normal flora. b. Opportunistic fungi can cause systemic mycoses in healthy and immunocompetent individuals even at low doses. c. Candida albicans can cause cutaneous Candidiasis when epithelial barrier functions are impaired. d. Rhizopus or Mucor spp. only cause Zygomycosis in severely immunocompromised patients.

B

10. Trichophyton verrucosum is a(n) ____________dermatophyte. a. Anthropophilic b. Zoophilic c. Geophilic

B.

13. Taxonomically, Pythium insidiosum is most accurately characterized as _________________. a. a fungus b. an oomycete c. a bacterium d. a plant

B.

20. The presence of many 2-4 μm organisms with a thin, non-staining cell wall inside macrophages suggests a fungal infection by _____ ? a. Cryptococcus neoformans b. Histoplasma capsulatum c. Blastomyces dermatitidis d. Coccidioides immitis

B.

23. Clinical situation: You submit a fungal culture on a nonhealing wound on a dog's foot. Five days later, the laboratory issues a report stating that they isolated Mucor spp. Because Mucor spp. is a common contaminant from the environment, you do the following: a. Immediately put the dog on an -azole antifungal drug b. Submit a biopsy for histopathology c. Submit a serum sample for detection of anti-Mucor antibodies d. Submit a urine sample for detection of galactomannan

B.

8. Microsporum canis is a(n) ______________ dermatophyte. a. Anthropophilic b. Zoophilic c. Geophilic

B.

22. Which of the following organism(s) are NOT opportunistic fungi? a. Candida albicans b. Cryptococcus neoformans c. Histoplasma capsulatum d. Rhizopus or Mucor spp.

C

11. Which of the following is a zoonotic infectious agent? a. Aspergillus fumigatus b. Histoplasma capsulatum c. Microsporum canis d. Coccidioides immitis

C.

14. Which of the following are the yeast forms of Sporothrix schenkii? a. Conidia b. Spherules c. Cigar bodies d. Arthrospores

C.

2. Which of the following drug targets Ergosterol in fungi membrane A. Flucytosine B. Griseofulvin C. Amphotericin B or Azoles (imidazole or Triazole ) D Echinocandins

C.

9. Microsporum gypseum is a(n) ______________ dermatophyte. a. Anthropophilic b. Zoophilic c. Geophilic

C.

A septae/non septae Hyphae

Co-enocytic (continues cells with many nuclei) -Thin walled, broad hyphae, sparse septa Primitive fungi- hyphal damage-> death -Grows & Spores rapidly Group - Zygomycetes

Describe the common features of opportunistic mycoses and the causative agents: Cryptococcosis

Cryptococcosis. a) Cryptococcosis is typically associated with feline nasal disease - ulcerative lesions affecting the mucous membranes of the upper respiratory tract (including nasal sinuses), or occasionally the central nervous system (meninges), and eyes (chorioretinitis). -Has been reported in several veterinary species including cats (most commonly affected), dogs, and horses. b) Causative agents: -Cryptococcus neoformans (in soil, enriched in pigeon droppings) and C. gatti (decaying wood of the red river gum), both grow as yeast in the environment and tissues. -They have a very thick capsule that is very characteristic of this fungus. c) Diagnosis: -Capsulated yeasts with narrow-based budding in cytologic preparations. d) Treatment with systemic antifungal agents; manage underlying immunosuppressive disease if possible.

12. Which of the following statement is TRUE? a. A negative Woods lamp test rules out dermatophytosis. b. A positive Woods lamp test provides a definitive diagnosis of dermatophytosis. c. The Woods lamp should not be allowed to warm-up prior to illuminating the patient. d. Trichophyton spp. rarely emit fluorescence under Wood's lamp illumination.

D

17. Which of the following species does not exhibit thermal dimorphism? a. Blastomyces dermatitidis b. Sporothrix schenkii C. Histoplasma capsulatum D. Coccidiodes immits

D

3. The differences between molds and yeasts can be characterized by _________________. a. Unicellular or multicellular b. Presence and morphology of hyphae c. Types of asexual reproduction (budding or spore formation) d. All of the above

D

15. Which of the following statement describing systemic mycosis is FALSE? a. Systemic mycosis is usually result from contact with dimorphic fungi present in the environment through inhalation. b. Systemic mycoses have distinct geographic distributions. c. Fungi causing systemic mycoses can grow as mold in the environment and as yeast or spherules in the host tissue. d. Systemic mycosis only occurs in immunosuppressed individuals.

D.

19. Where may Blastomyces dermatitidis disseminate following initial infection? a. Eye b. Bone c. Brain d. All of the above

D.

5. Which of the following statement describing current fungi classification is FALSE? a. Historically, fungi are classified based on their morphological characteristics and spore production. b. Current fungi taxonomy is based on molecular phylogenetic approaches (sequence alignment and phylogenetic analysis of 18S rRNA genes). c. Even in the absence of the teleomorph, anamorphic molds (Deuteromycota) can be possibly assigned to Ascomycota or Basidiomycota based on DNA sequences of anamorphs. d. Deuteromycota ("Fungi Imperfecti") is an officially recognized taxonomic group.

D.

6. Host factors are extremely important in the establishment of localized fungal infections. Which of the following best describes the important host factor(s)? a. Skin trauma or prolonged moisture b. Decreased colonization resistance due to loss of local bacteria c. Local immunosuppression due to topical corticosteroid administration d. All of the above

D.

7. Why deep mycoses are not caused by most fungal pathogens? a. Healthy, immunocompetent animals is capable of eliminating most fungal pathogens. b. Most fungi are aerobes with optimal growth temperature at 25-30°C, therefore do not multiply well in the body. c. Most fungi have low invasiveness and low virulence potentials. d. All of the above

D.

Describe Epidemiologic, clinical , *DX and *TX aspects of dermatophytosis and Malassezia dermatitis in Vet species

Diagnosis : is typically based on clinical observations and cytology examination: presence of characteristic "shoe print" pattern of oval budding yeasts with a single bud attached by a broad base. • For treatment: correction of the underlying condition is the most important aspect of treatment of M. pachydermatis-associated otitis externa or dermatitis. Almost all commercially available anti-fungal topical preparations are effective in treating Malassezia infections.

Structure of fungi

Most are aerobes or Facultative anaerobes Cell walls are Ridgid: contain CHITIN , Mannan and other polysacc's Cytoplasmic membrane contain : ERGOSTEROLS (only in fungi)

Anti-fungal agents

Target fungi specific parts or metabolic pathways -Ployene antibiotics (** Amphotericin B and Nystaitin ) -Bind Ergosterol -Azoles (imidazole and Triazoles ) -Ergosterol biosynthesis

Fungal Morphology

Yeast (unicellular ) Yeast like Molds -multicellular Dimorphic fungi- can switch form

Describe the common features of opportunistic mycoses and the causative agents: Zygomycosis

Zygomycosis. a) Most common form: Mucormycosis. The major causative agents are Rhizopus, Mucor, Absidia spp., which are common contaminants from the environment as thermotolerant saprophytes in soil and decaying vegetation. -These zygomycetes have broad hyaline, non-septate hyphae, and sporangium with sporangiophores b) Infection : -mainly by inhalation or ingestion (lymph nodes of respiratory and alimentary tracts). -Only in severely immunocompromised patients, and are frequently secondary to concurrent infections or metabolic acidosis. -Cause deep, progressive, and rapidly invasive subcutaneous mycosis. -Ulcerated cutaneous granulomas also found in stomach and intestines. c) Diagnosis: -Histopathology more reliable than culturing. -Distinctive infrequently septate, thin-walled broad hyphae with focal bulbous dilations and irregular branching in smears or stained tissue sections from lesions and biopsies. -Occasionally, sporangium with sporangiophores can be seen. d) Treatment: High doses of intravenous Amphotericin B is the preferred drug; surgical interventions may be necessary.

Describe *Epidemiologic, *clinical , DX and TX aspects of dermatophytosis and Malassezia dermatitis in Vet species

a. Dermatophytosis, also known as "tinea" or "ringworm", is a common skin disorder caused by an infection of a dermatophyte. Dermatophytosis, and Malassezia otitis and dermatitis, represent the superficial mycoses of greatest significance in companion and farm animal health. b. The dermatophytes consist of a group of fungi that are adapted to digest keratinous debris; when pathogenic, they are normally located in the epidermal stratum corneum, hair shaft, or claw. Dermatophytes that are adapted to animal hosts are termed "zoophilic", such as Microsporum canis. The soil-adapted "geophilic" dermatophytes, e.g. Microsporum gypseum, sometimes affect animals where there is outdoor husbandry or activity. Microsporum spp. and Trichophyton spp. account most of the animal diseases, and the human-adapted "anthropophilic" species, such as Epidermophyton floccosum, are predominantly found on humans. c. Common etiological agents. • Microsporum canis is a zoophilic dermatophyte best adapted to the cat. It was the most frequent cause of dermatophytosis in cats and dogs in the US, and occasionally, can be spread to humans or other animals while in contact (zoonotic). • Trichophyton spp. are common genus infecting large animals: T. equinum and T. mentagrophytes are most common in horses, whereas T. verrucosum dermatophytosis is enzootic in many cattle herds. Microsporum gypseum is the mostfrequent dermatophyte of horses, and often associated with canine ringworm in the southern USA. d. Dermatophytoses should be suspected in animals with skin lesions comprising combinations of alopecia, erythema, papules, scaling, and crusting. e. The principal diagnostic methods are Wood's lamp examination (false positive and negative resultslikely; Trichophyton spp. rarely emit fluorescence), direct microscopy, culture (Sabouraud's agar, and Dermatophyte Test Medium/DTM), and biopsy. The first three tests should be considered complementary and should be routinely performed. Microscopic examination shows the presence of septate hyphae and arthroconidia (macro- and/or microconidia). f. The normal course of mammalian dermatophytosis is self-cure within 1 to 4 months. Topical therapy is of particular value in targeting surface fungi. Griseofulvin is the most commonly used systemic treatment for dermatophytosis in small animals. Alternatively, systemic treatments with oral ketoconazole and itraconazole are used. g. Malassezia pachydermatis is the normal inhabitant of skin and external ear canals (dogs/cats). As an opportunistic pathogen, infections (otitis externa and dermatitis in dogs and cats) are due to other primary problems.

Describe the general features, classification and antifungal chemotherapy for fungal Dz's

a. Mycosis is a disease caused by a fungus. Fungi, excepting the dermatophytes, rarely cause diseases in healthy, immunocompetent animals. Disease usually results from debilitating conditions favoring fungi growth or host barriers accidentally penetrated by fungi, including loss of normal cutaneous barriers or bacterial flora, and immunosuppression by topical steroids treatment. b. Fungal diseases may be grouped in several ways. Opportunistic fungi seldom cause disease without some underlying predisposing factor, such as trauma or immunosuppression. Pathogenic fungi cause disease without a predisposing factor, which can be grouped into the superficial or cutaneous, subcutaneous, and systemic mycoses. c. Superficial and cutaneous mycoses (dermatomycoses) are associated with hair, nails, and keratinized layers of the skin. Subcutaneous mycoses affect mainly dermis, bone, muscle, and fascia. Systemic mycoses represent a group of fungi that invade internal organs following hematogenous dissemination from the lungs. D. Most of the fungi produce Dz's characterized by inflammation & Granulomatous lesions. -Mycoses should be included in the differential Dx of any chronic condition that have failed to respond to TX for which the cause is unknown. E. TX of particular fungal Dzs varies -However, several RX's target fungal Membrane component (Ergosterol) have considerable anti fungal activity, including POLYENE Antibiotics (Amphotericin B and Nystatin ) and Azoles (ex: fluconazole and itraconazole) fungicides

Describe the general characteristics & etiological agents causing Subcutaneous Mycoses

a. Subcutaneous mycoses are chronic, suppurative or granulomatous infections of the subcutaneous tissues, usually on an extremity (hands, feet); can extend through the lymphatics or sinus tracts. Caused by dimorphic fungi or fungus-like microbes. b. Sporotrichosis is caused by a thermal dimorphic fungus Sporothrix schenkii that lives in soil and on plant matter. Sporotrichosis is more frequently reported in humans ("Rose gardener's disease"), horses, dogs, and cats in endemic areas like central/south America (zoonotic!). —a) Most cats with Sporotrichosis will develop cutaneolymphatic or disseminated disease regardless of their immune status. —b) Direct examination of exudates is often unrewarding except with feline specimens or specimens from immune compromised patients, where organisms are present in the cytologic preparation with the classic oval to cigar-shaped yeast forms ("cigar bodies"). —c) Culturing on Sabouraud's agar will demonstrate hyphae and microconidia with characteristic "flowerette" arrangement. —d) Treatment: The cutaneous form responds generally to the oral administration of sodium or potassium iodides. The azole drugs, especially itraconazole and ketoconazole, are effective. c. Pythiosis (aka "Swamp Cancer" and "Florida Horse Leeches") is a chronic ulcerative fibro- or pyo-granulomatous, and eosinophilic cutaneous and subcutaneous lesions in horses, cattle, dogs, and cats, and gastrointestinal disease in dogs. —a) Caused by the soil-borne Pythium insidiosum, an aquatic oomycete (pseudo-fungus) which is endemic in some tropical and subtropical areas with warm stagnant water. —b) Common diagnostic method is cytology: broad, poorly septate, and branching hyphal elements are seen among the pyogranulomatous and eosinophilic inflammation. —c) Early diagnosis is the key to successful treatment. Treatments include surgery and antifungal therapy (amphotericin B and -azoles)

What is the common features of systemic mycosis and its etiological agents ?

a. Systemic mycoses result from contact with fungi in the environment, especially through inhalation. -They disseminate and cause deeper infection of the tissues, blood, and organ systems, often create symptoms resembling other diseases. B. All etiological agents are dimorphic /diphasic fungi that grow as mold in environment and as yeast or spherules in the host tissue -they have distinct geographic distributions and immunosuppression is NOT a requirement for infection c. **Histoplasmosis: - is an infection of the reticuloendothelial system resulting in patchy bronchopneumonia containing yeast-laden phagocytic cells within alveolar spaces. -The yeast cells multiply within the giant cells produced and can disseminate to other tissues. —a) Caused by a thermally dimorphic fungus - Histoplasma capsulatum, which is endemic in the Mississippi and Ohio River valleys, and enriched in bird and bat droppings. —b) Common diagnostic method is cytology: many 2-4 μm organisms with a thin, nonstaining cell wall that are consistent with Histoplasma capsulatum are present in phagocytes (macrophages and/or neutrophils) of a cytologic smear. d.** Blastomycosis** - is a common mycosis of dogs in the United States. -Blastomycosis is usually a chronic or systemic granulomatous disease, which originates primarily as a respiratory tract infection. -Dissemination to skin, abdominal viscera, bone, and brain can occur. —a) Caused by a thermally dimorphic fungus - Blastomycosis dermatitidis. -The saprophytic form grows in acidic, moist soil that is endemic in Eastern and Midwestern US. —b) Common diagnostic methods are cytology (presence of yeast with thick double-contoured wall and broad-based budding), culture (presence of septate hyphae, microcondia, and chlamydospores), or serology. e. Coccidioidomycosis: - is only found in lower elevation desert areas of the Southwest USA. -The most common site of infection is the lung, but cutaneous infections may result. -The disease usually results in a benign, self-limiting condition of the respiratory tract. -Less common are chronic fulminating granulomatous reactions. In disseminated cases, the disease extends to other visceral organs, bones, joints, and to the skin (most susceptible in the boxer dogs). —a) Caused by a tissue dimorphic fungus (temperature independent!) - Coccidioides immitis: as a mold (hyphae with arthrospores - highly infectious!) in soil and as a spherule (with endospores) in tissue. -The spherule causes a giant cell granulomatous reaction in the host. After release, the endospores cause a pyogenic reaction with surrounding neutrophils. —b) Diagnosis by Cytology & Histopathology - presence of spherules in animal fluids or tissue.

septate hyphae

contain cross-walls

Mycosis

fungal infection -wide variety of DZ -frequenters DX mysteries -mimic other Dz: neoplasia or Granulomatous DZ, inflammation